Roles and ClusterRoles in Kubernetes - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a Role in Kubernetes?

A Role defines permissions within a specific namespace. It controls what actions a user or service can perform on resources inside that namespace.

beginner

What is a ClusterRole in Kubernetes?

A ClusterRole defines permissions across the entire cluster or can be used in any namespace. It controls actions on cluster-wide resources or multiple namespaces.

intermediate

How does a Role differ from a ClusterRole?

A Role is limited to one namespace, while a ClusterRole applies cluster-wide or to multiple namespaces. ClusterRoles can also grant access to cluster-scoped resources.

intermediate

What is the purpose of RoleBinding and ClusterRoleBinding?

RoleBinding assigns a Role to users or groups within a namespace. ClusterRoleBinding assigns a ClusterRole to users or groups cluster-wide or across namespaces.

intermediate

Can a ClusterRole be used in a single namespace?

Yes, a ClusterRole can be bound to a user or group in a specific namespace using a RoleBinding, allowing cluster-wide permissions to be applied locally.

What scope does a Kubernetes Role apply to?

A The entire cluster

B A single namespace

C Multiple clusters

D Only system namespaces

A Role applies permissions only within a single namespace.

Which Kubernetes object grants cluster-wide permissions?

A Role

B Namespace

C RoleBinding

D ClusterRole

ClusterRole grants permissions across the entire cluster.

How do you assign a ClusterRole to a user in a specific namespace?

A Using ClusterRoleBinding

B Using NamespaceBinding

C Using RoleBinding

D Using PodSecurityPolicy

RoleBinding can bind a ClusterRole to a user within a specific namespace.

Which object is used to bind a Role to a user?

A RoleBinding

B ClusterRoleBinding

C ServiceAccount

D Pod

RoleBinding assigns a Role to users or groups within a namespace.

Can a Role grant permissions on cluster-scoped resources?

A No, Roles are namespace-scoped

B Yes, always

C Only if combined with ClusterRole

D Only in system namespaces

Roles cannot grant permissions on cluster-scoped resources because they are limited to namespaces.

Explain the difference between a Role and a ClusterRole in Kubernetes.

Think about where each permission applies.

Describe how RoleBinding and ClusterRoleBinding are used to assign permissions.

Focus on how permissions are linked to users.

Practice

1. What is the main difference between a Role and a ClusterRole in Kubernetes?

easy

A. Role applies permissions within a single namespace, ClusterRole applies cluster-wide.

B. Role applies cluster-wide, ClusterRole applies within a single namespace.

C. Role is for users, ClusterRole is for service accounts only.

D. Role manages nodes, ClusterRole manages pods.

Solution

1. Step 1: Understand Role scope

   A Role defines permissions limited to a specific namespace in Kubernetes.

2. Step 2: Understand ClusterRole scope

   A ClusterRole defines permissions that can apply across all namespaces or cluster-wide resources.

3. Final Answer:

   Role applies permissions within a single namespace, ClusterRole applies cluster-wide. -> Option A

4. Quick Check:

   Role = namespace, ClusterRole = cluster-wide [OK]

Hint: Role = namespace only, ClusterRole = whole cluster [OK]

Common Mistakes:

• Confusing Role and ClusterRole scopes
• Thinking ClusterRole is only for nodes
• Assuming Role applies cluster-wide

2. Which of the following is the correct YAML snippet to create a Role that allows reading pods in a namespace?

easy

A. apiVersion: rbac.authorization.k8s.io/v1\nkind: Role\nmetadata:\n name: pod-reader\nrules:\n- apiGroups: ['']\n resources: ['pods']\n verbs: ['get', 'watch', 'list']

B. apiVersion: rbac.authorization.k8s.io/v1\nkind: ClusterRole\nmetadata:\n name: pod-reader\nrules:\n- apiGroups: ['']\n resources: ['pods']\n verbs: ['create', 'delete']

C. apiVersion: rbac.authorization.k8s.io/v1\nkind: RoleBinding\nmetadata:\n name: pod-reader-binding\nroleRef:\n kind: Role\n name: pod-reader\nsubjects:\n- kind: User\n name: alice

D. apiVersion: rbac.authorization.k8s.io/v1\nkind: Role\nmetadata:\n name: pod-reader\nrules:\n- apiGroups: ['apps']\n resources: ['pods']\n verbs: ['get', 'watch', 'list']

Solution

1. Step 1: Check kind and apiVersion

   The resource is a Role with apiVersion rbac.authorization.k8s.io/v1, which is correct for RBAC.

2. Step 2: Verify rules for reading pods

   Pods are in the core API group (empty string), and verbs for reading are get, watch, and list. apiVersion: rbac.authorization.k8s.io/v1\nkind: Role\nmetadata:\n name: pod-reader\nrules:\n- apiGroups: ['']\n resources: ['pods']\n verbs: ['get', 'watch', 'list'] matches this exactly.

3. Final Answer:

   The YAML snippet with kind: Role, apiGroups: [''], resources: ['pods'], verbs: ['get', 'watch', 'list']. -> Option A

4. Quick Check:

   Role + core API + read verbs = apiVersion: rbac.authorization.k8s.io/v1\nkind: Role\nmetadata:\n name: pod-reader\nrules:\n- apiGroups: ['']\n resources: ['pods']\n verbs: ['get', 'watch', 'list'] [OK]

Hint: Role for namespace, core API group is empty string [''] [OK]

Common Mistakes:

• Using ClusterRole instead of Role for namespace scope
• Wrong apiGroups value like 'apps' for pods
• Confusing RoleBinding with Role definition

3. Given this RoleBinding YAML snippet, what namespace will the binding apply to?

apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: read-pods
  namespace: dev
roleRef:
  kind: Role
  name: pod-reader
  apiGroup: rbac.authorization.k8s.io
subjects:
- kind: User
  name: jane

medium

A. default namespace

B. Cluster-wide

C. kube-system namespace

D. dev namespace

Solution

1. Step 1: Check metadata namespace in RoleBinding

   The RoleBinding has namespace: dev in its metadata, so it applies in the 'dev' namespace.

2. Step 2: Understand RoleBinding scope

   RoleBindings are namespace-scoped, so they only apply in the namespace where they are created.

3. Final Answer:

   The RoleBinding applies to the dev namespace. -> Option D

4. Quick Check:

   RoleBinding namespace = binding scope [OK]

Hint: RoleBinding namespace field sets scope [OK]

Common Mistakes:

• Assuming RoleBinding applies cluster-wide
• Confusing RoleBinding with ClusterRoleBinding
• Ignoring the metadata namespace field

4. You created a ClusterRoleBinding but users report they cannot access cluster resources. Which is the most likely mistake?

medium

A. The subjects field is missing the user names.

B. The roleRef kind is set to Role instead of ClusterRole.

C. The ClusterRoleBinding is created in a namespace.

D. The apiVersion is set to v1 instead of rbac.authorization.k8s.io/v1.

Solution

1. Step 1: Check roleRef kind for ClusterRoleBinding

   A ClusterRoleBinding must reference a ClusterRole in its roleRef.kind. Using Role is invalid and prevents access.

2. Step 2: Verify other fields

   While missing subjects or wrong apiVersion cause issues, the most common cause is wrong roleRef.kind. ClusterRoleBindings are cluster-scoped and do not belong to namespaces.

3. Final Answer:

   The roleRef kind must be ClusterRole, not Role. -> Option B

4. Quick Check:

   ClusterRoleBinding needs ClusterRole in roleRef [OK]

Hint: ClusterRoleBinding must reference ClusterRole kind [OK]

Common Mistakes:

• Using Role instead of ClusterRole in roleRef
• Creating ClusterRoleBinding in a namespace
• Forgetting to specify subjects

5. You want to allow a user to list pods in all namespaces but only create pods in the 'test' namespace. Which combination of Kubernetes RBAC objects should you create?

hard

A. A ClusterRoleBinding granting create pods cluster-wide.

B. A single Role with both permissions in the 'test' namespace.

C. A ClusterRole with list pods permission and a Role with create pods permission, plus respective bindings.

D. A RoleBinding in 'test' namespace granting list and create pods.

Solution

1. Step 1: Understand permission scopes

   Listing pods in all namespaces requires a ClusterRole because it is cluster-wide permission.

2. Step 2: Restrict create pods to 'test' namespace

   Creating pods only in 'test' namespace requires a Role scoped to that namespace.

3. Step 3: Bind roles to user

   Use a ClusterRoleBinding for the cluster-wide list permission and a RoleBinding for the create permission in 'test'.

4. Final Answer:

   Create a ClusterRole for list pods and a Role for create pods with bindings. -> Option C

5. Quick Check:

   ClusterRole = cluster-wide, Role = namespace [OK]

Hint: Use ClusterRole for cluster-wide, Role for namespace-specific [OK]

Common Mistakes:

• Trying to use a single Role for cluster-wide permissions
• Using ClusterRoleBinding for namespace-only permissions
• Not creating separate bindings for each role